The present invention relates to fin stocks for use in a heat exchanger made of aluminum alloy and more particularly to fin stocks for use in a heat exchanger made of aluminum alloy, which are resistant to drooping and serve as sacrificial anodes. The present invention also relates to a method for producing such fin stocks.
Conventionally, in an aluminum air-cooled heat exchanger, a brazing sheet comprising a core metal layer made of aluminum of corrosion-resistant aluminum alloy and a cladding metal layer made of Al-Si-base alloy or Al-Si-Mg base alloy formed on the core metal layer is applied to either a fluid passage member (tube or section) the cooling fins on the air side. However, when exposed to a severely corrosive atmosphere, pitting corrosion occurs in the wall of the heat exchanger on the air side by corrosion so that the fluid is apt to leak from the holes. Therefore, various surface processing methods for preventing such corrosion have been investigated and are used in practice. However, there is no perfect anticorrosion method. Some of the conventional methods are comparatively good, but have some problems from the economical point of view.
Furthermore, it is proposed that a material having a sacrificial anode effect be used in fin stocks for use in an aluminum air-cooled heat exchanger. As the conventional material for the sacrificial anode, AA7072 alloy is known. However, when AA7072 alloy is soldered in vacuum or under reduced pressure, Zn is evaporated and the sacrificial anode effect of the AA7072 alloy is not only reduced, but also the chamber for soldering is smeared or damaged by the evaporated alloy.